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Determination of pH

  The pH value in different types of samples is determined by a portable digital pHmeter. The principle of the determination is based on potentiometry. Thee pHmeter has a pH combination electrode and pH values can be estimated in the range of 0.00 to 14.00 with a resolution of 0.01 and accuracy of 0.01.

Instructions

  1/ Connect the pHmeter with the pH electrode and switch. Set the mode switch to thr pH

  position. This will activate the liquid cristal display. Condition the electrode in buffer 7.00

until the display is fully stable (about 30 minutes). Give a stirring action to the electrode each time it is placed in a new solution.

  2/ Adjust the calibration control to make the display read the value of buffer 7.00. Rinse the electrode with distilled water and blot dry.

  3/ Inmerse the electrode in buffer 4.00. When the display is stable (30 seconds), adjust the  slope control to make the display read the value of buffer 4.00. The pH value are 6.99 and   4.01 for buffer 7.00 and 4.00 respectively at 30oC. Error may be minimum in the case that

    pH value are not adjust to the temperature of the solution to be tested.

     The apparatus is now calibration to read samples with pH 0 - 14.

  4/ Rinse the electrode with distill water, blot dry and inmerse in the saple. The sample must

    be homogenous. When the display is stable (30 seconds), it will read the pH of the sample

    Repeat this step for continued samples. Periodically check calibration, at least one per day.

  5/ When all samples are completed, keep the electrode inmerse in distilled water. The

    electrode shall never be kept dry, otherwise electrode damage shall be irreversible.

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